The use of scarfing rolls or their equivalents to meter fibers is commonly known industrial practice. For example, U.S. Pat. No. 2,635,301 teaches a mat forming device for wood fibers wherein a rotor having a plurality of tines is used to determine the thickness of the mat. U.S. Pat. No. 2,919,475 teaches a similar function for a process using various forms of wood materials for making fiberboard, wherein a spiked leveling roll is used to obtain a precise thickness. The materials scraped off are conveyed back to the feed hopper for recycle. U.S. Pat. No. 3,016,582 teaches a batt forming apparatus which uses a leveling rotor having four equally spaced vanes rather than individual tines or spikes. U.S. Pat. No. 4,091,161 teaches a dry-forming process for nonwoven webs wherein a rotating peak removal device consisting of a double comb rotating in the direction of the web removes excess material and directs it to recycle. U.S. Pat. No. 4,218,414 teaches an air-laying process wherein a peg roller is used to control the thickness of the batt. The excess fibers removed by the roller are thrown back and mixed with feed fibers.
Although all of these devices may work well for the specific processes in which they are used, it is believed such devices would not perform well in practice when used alone for the formation of uniform basis weight air-laid batts of wood fibers suitable as a feed for making light basis weight products such as facial tissue. For such processes, the basis weight of the batt must be extremely uniform to avoid quality defects in the final product. Without such uniformity it would be necessary to produce a heavier-than-necessary product to ensure that the thinnest spots in the batt are of adequate thickness to provide sufficient strength. Such over-designed products carry an economic penalty because of the unnecessarily high basis weight. Because the nature of such products requires high speed production at low cost, it is necessary that any metering devices used be effective, reliable, and inexpensive to operate.